This invention relates to a semiconductor component for the generation of optical radiation and with a region of p-type material, a region of n-type material and a p-n junction between the said regions, the p-n junction having a radiation-emitting active portion.
Generally speaking, light-emitting diodes (LEDs) are used for transforming electrical energy into optical energy. A normal operating current for an LED is 10-100 mA. At these current intensities, the efficiency of hitherto designed components, generally speaking, is high. For infrared emitting structures an internal quantum efficiency in the range of 80-90% is not unusual in commercially available LEDs. However, at low currents through the diode, for example 10 .mu.A, the quantum efficiency drops drastically and is often at permillage level. The reason for the poor efficiency of these low currents, is that the charge transport through the component is dominated by current along the surface of the component, which does not give rise to any light emission.
In many applications, however, it could be very important to be able to use light-emitting components which have a high efficiency at low currents. One example of such an application is a fiber optic measuring system, in which energising power to operate a measuring transducer is only supplied thereto via optical fibers. The measuring signal from such a measuring transducer is usually transmitted back through the fiber system by means of an optical signal generated, for example, by an LED. For driving such an LED, only limited power is available and the total performace of the system is often determined by the efficiency of the LED. An example of this type of application is given in published European patent application No. 0 041 668.
One further example of the usefulness of a component with the performance mentioned above is two-way optical communication between stations via fibers, where one station has no other power supply than that supplied optically via the fiber. Such a system is proposed, in part, in the publication "The Bell System Technical Journal", vol. 57, No. 11, November 1978, page 3309.